Tetracyclines

Question 1

Tetracycline
(Inhibition of Protein Synthesis - bacteriostatic)
(Broad Spectrum)
(Strept, MSSA, MRSA, Chlamydia, Mycoplasma pneumoniae, E coli)

Answer 1

Reversibly binds 30S subunit, blocking tRNA entry on ribosome
Admin: Oral w/out food (esp milk)
Penetrates all tissues, including placenta
Renal Excretion
Now ineffective on most gram +/- bacteria

Question 2

Doxycycline
(Inhibition of Protein Synthesis - bacteriostatic)
(Broad Spectrum)
(Strept, MSSA, MRSA, Chlamydia, Mycoplasma pneumoniae, E coli)

Answer 2

Reversibly binds 30S subunit, blocking tRNA entry on ribosome
Admin: Oral w/out food (esp milk)
Penetrates all tissues, including placenta
Hepatic Excretion

Question 3

Resistance

Answer 3

Changes in transport in and out of cells; proteins that block tetracycline binding (MDR)

Question 4

Side Effects and Drug Interactions

Answer 4

SE: Temp. depression of bone growth, nausea, vomiting, diarrhea, photosensitivity, yeast overgrowth, liver/kidney toxicity
DI: Bioavailability lowered by antacids and Fe supplements, increased anticoagulant effect, Phenytoin/Barbiturates/Carbamazepine –> increases Doxy metabolism